I had a tie dye party with some friends a while back. Are all the kids 9-ish? If they are then - great! If not, you will definitely want some help if you have younger kids. Have plenty of cardboard. It does get messy. Absolutely you will want gloves. I would suggest having the dye in squirt bottles as opposed to having them in containers with little squeeze things (the name of which escapes me this late at night!!!). I would also suggest having whatever they're going to dye soaking in the solution before then arrive instead of waiting to put it in when they're there. Have lots of rubber bands available. I would also suggest having white bags with their names already on them to put the tie dyed stuff into. Are you going to send the stuff home with the kids to wash out later, or are you going to keep it all there to wash out together later (If you are, don't forget to make the kids things somehow!)? If so, I would suggest having some kind of big plastic tub that you can take outside - take all the shirts (or whatever) out of the bags and take off the rubber bands and put them in the plastic tub - then take the tub inside and dump it into the washing machine. I suggest that because if you open the bags and take off the bands inside - the dye tends to splatter. Good luck - it sounds like a fun birthday party. The kids I've done tie dye with loved it!